This application seeks renewal of a program, currently in its tenth year of support, to train post-doctoral, pediatric physician and non-physician trainees in basic immunology side-by-side in the rich, shared environment of the Department of Immunology at the University of Washington; five positions are requested. This represents a joint venture between the Department of Immunology and the Division of Pediatric Immunology, Infectious Diseases and Rheumatology. Physician and non-physician trainees complement each other: The physician investigators bring to the program unique perspectives derived from direct interaction with patients and laboratory research experience of varying degrees. The non-physician, Ph.D. trainees bring to the program a rich background of didactic and laboratory research experience, but limited familiarity with the potential clinical ramifications of their work. The key quality sought in all trainees is a clear commitment to and outstanding potential for research. Training consists of laboratory research under the mentorship of a member of the training faculty, course work and other informal training experiences for a period of three or more years. A formal course in the responsible conduct of research is included. The ultimate goal of the program is to develop the next generation of investigators, who will make important contributions to our understanding of fundamental immunology and of normal and abnormal immune function relevant to human immunological and infectious diseases. This is a particularly timely goal, since we are now at a juncture when the application of immunological principles derived from fundamental research to human biology and disease is at hand, as witnessed by the advent of programs such as the immune tolerance network, the rational development of new vaccines and other forms of human immunotherapeutics.